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121-459: The smaller Cascade and Crillon glaciers and the larger Lituya Glacier all spill into Lituya Bay, which is a part of Glacier Bay National Park and Preserve . Cenotaph Island is located roughly in the middle of the bay. The entrance of the bay is approximately 500 m (0.31 mi) wide, with a narrow navigable channel. The bay is known for its tremendous size tides , which have a range of approximately 3 m (9.8 ft). Tidal currents in

242-424: A cirque landform (alternatively known as a corrie or as a cwm ) – a typically armchair-shaped geological feature (such as a depression between mountains enclosed by arêtes ) – which collects and compresses through gravity the snow that falls into it. This snow accumulates and the weight of the snow falling above compacts it, forming névé (granular snow). Further crushing of the individual snowflakes and squeezing

363-522: A glacier is usually assessed by determining the glacier mass balance or observing terminus behavior. Healthy glaciers have large accumulation zones, more than 60% of their area is snow-covered at the end of the melt season, and they have a terminus with a vigorous flow. Following the Little Ice Age 's end around 1850, glaciers around the Earth have retreated substantially . A slight cooling led to

484-601: A glacier may flow into a body of water, it forms only on land and is distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water. On Earth, 99% of glacial ice is contained within vast ice sheets (also known as "continental glaciers") in the polar regions , but glaciers may be found in mountain ranges on every continent other than the Australian mainland, including Oceania's high-latitude oceanic island countries such as New Zealand . Between latitudes 35°N and 35°S, glaciers occur only in

605-411: A glacier via moulins . Streams within or beneath a glacier flow in englacial or sub-glacial tunnels. These tunnels sometimes reemerge at the glacier's surface. Most of the important processes controlling glacial motion occur in the ice-bed contact—even though it is only a few meters thick. The bed's temperature, roughness and softness define basal shear stress, which in turn defines whether movement of

726-638: A height measuring 1,719 feet (524 m), taller than the Empire State Building . There were three fishing boats anchored near the entrance of Lituya Bay on the day the giant wave occurred. One boat (the Sunmore ) was sunk by the wave and debris as it attempted to exit the bay, and the two people on board (a married couple, the Wagners) were killed. The second boat (the Badger ) was carried across

847-555: A higher potential for larger, high-magnitude earthquakes in the future. The mountain range is also a source of shallow intraplate earthquakes within the South American Plate. The largest such earthquake (as of 2024) struck Peru in 1947 and measured M s   7.5. In the Peruvian Andes, these earthquakes display normal ( 1946 ), strike-slip (1976), and reverse ( 1969 , 1983) mechanisms. The Amazonian Craton

968-566: A joint ice stream network. The Andes' dendritic glacier arms, components of valley glaciers, were up to 112.5 km (69.9 mi) long and over 1,250 m (4,101 ft) thick, and spanned a vertical distance of 5,150 m (16,896 ft). The climatic glacier snowline (ELA) was lowered from 4,600 m (15,092 ft) to 3,200 m (10,499 ft) at glacial times. The Andean region cuts across several natural and floristic regions, due to its extension, from Caribbean Venezuela to cold, windy, and wet Cape Horn passing through

1089-408: A kilometer per year. Eventually, the ice will be surging fast enough that it begins to thin, as accumulation cannot keep up with the transport. This thinning will increase the conductive heat loss, slowing the glacier and causing freezing. This freezing will slow the glacier further, often until it is stationary, whence the cycle can begin again. The flow of water under the glacial surface can have

1210-404: A large effect on the motion of the glacier itself. Subglacial lakes contain significant amounts of water, which can move fast: cubic kilometers can be transported between lakes over the course of a couple of years. This motion is thought to occur in two main modes: pipe flow involves liquid water moving through pipe-like conduits, like a sub-glacial river; sheet flow involves motion of water in

1331-460: A lower heat conductance, meaning that the basal temperature is also likely to be higher. Bed temperature tends to vary in a cyclic fashion. A cool bed has a high strength, reducing the speed of the glacier. This increases the rate of accumulation, since newly fallen snow is not transported away. Consequently, the glacier thickens, with three consequences: firstly, the bed is better insulated, allowing greater retention of geothermal heat. Secondly,

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1452-594: A north–south axis of cultural influences. A long series of cultural development culminated in the expansion of the Inca civilization and Inca Empire in the central Andes during the 15th century. The Incas formed this civilization through imperialistic militarism as well as careful and meticulous governmental management. The government sponsored the construction of aqueducts and roads in addition to pre-existing installations. Some of these constructions still exist today. Devastated by European diseases and by civil war ,

1573-711: A series of bends or oroclines . The Bolivian Orocline is a seaward-concave bending in the coast of South America and the Andes Mountains at about 18° S. At this point, the orientation of the Andes turns from northwest in Peru to south in Chile and Argentina . The Andean segments north and south of the Orocline have been rotated 15° counter-clockwise to 20° clockwise respectively. The Bolivian Orocline area overlaps with

1694-488: A thin layer. A switch between the two flow conditions may be associated with surging behavior. Indeed, the loss of sub-glacial water supply has been linked with the shut-down of ice movement in the Kamb ice stream. The subglacial motion of water is expressed in the surface topography of ice sheets, which slump down into vacated subglacial lakes. The speed of glacial displacement is partly determined by friction . Friction makes

1815-410: A tremendous impact as the iceberg strikes the water. Tidewater glaciers undergo centuries-long cycles of advance and retreat that are much less affected by climate change than other glaciers. Thermally, a temperate glacier is at a melting point throughout the year, from its surface to its base. The ice of a polar glacier is always below the freezing threshold from the surface to its base, although

1936-634: A typical location for calc-alkalic and subduction volcanism, the Andean Volcanic Belt has a large range of volcano-tectonic settings, such as rift systems, extensional zones, transpressional faults , subduction of mid-ocean ridges , and seamount chains apart from a large range of crustal thicknesses and magma ascent paths, and different amount of crustal assimilations. The Andes Mountains host large ore and salt deposits, and some of their eastern fold and thrust belts act as traps for commercially exploitable amounts of hydrocarbons . In

2057-536: A whole glacier in the ablation area or in the accumulation area . In the high Andes of Central Chile and Mendoza Province , rock glaciers are larger and more common than glaciers; this is due to the high exposure to solar radiation . In these regions, glaciers occur typically at higher altitudes than rock glaciers. The lowest active rock glaciers occur at 900 m a.s.l. in Aconcagua . Though precipitation increases with height, there are semiarid conditions in

2178-780: A zone of volcanic activity that encompasses the Pacific rim of the Americas as well as the Asia-Pacific region. The Andes are the result of tectonic plate processes extending during the Mesozoic and Tertiary eras, caused by the subduction of oceanic crust beneath the South American Plate as the Nazca Plate and South American Plate converge. These processes were accelerated by the effects of climate. As

2299-561: Is a result of the subduction of the Nazca Plate and Antarctic Plate underneath the South American Plate. The belt is subdivided into four main volcanic zones that are separated from each other by volcanic gaps. The volcanoes of the belt are diverse in terms of activity style, products, and morphology. While some differences can be explained by which volcanic zone a volcano belongs to, there are significant differences inside volcanic zones and even between neighboring volcanoes. Despite being

2420-456: Is above or at freezing at the interface and is able to slide at this contact. This contrast is thought to a large extent to govern the ability of a glacier to effectively erode its bed , as sliding ice promotes plucking at rock from the surface below. Glaciers which are partly cold-based and partly warm-based are known as polythermal . Glaciers form where the accumulation of snow and ice exceeds ablation . A glacier usually originates from

2541-551: Is actively underthrusted beneath the sub-Andes region of Peru, producing thrust faults. In Colombia, Ecuador, and Peru, thrust faulting occurs along the sub-Andes due in response to compression brought on by subduction, while in the high Andes, normal faulting occurs in response to gravitational forces. In the extreme south, a major transform fault separates Tierra del Fuego from the small Scotia Plate . The Andes range has many active volcanoes distributed in four volcanic zones separated by areas of inactivity. The Andean volcanism

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2662-407: Is affected by factors such as slope, ice thickness, snowfall, longitudinal confinement, basal temperature, meltwater production, and bed hardness. A few glaciers have periods of very rapid advancement called surges . These glaciers exhibit normal movement until suddenly they accelerate, then return to their previous movement state. These surges may be caused by the failure of the underlying bedrock,

2783-411: Is because these peaks are located near or in the hyperarid Atacama Desert . Glaciers erode terrain through two principal processes: plucking and abrasion . As glaciers flow over bedrock, they soften and lift blocks of rock into the ice. This process, called plucking, is caused by subglacial water that penetrates fractures in the bedrock and subsequently freezes and expands. This expansion causes

2904-406: Is by basal sliding, where meltwater forms between the ice and the bed itself. Whether a bed is hard or soft depends on the porosity and pore pressure; higher porosity decreases the sediment strength (thus increases the shear stress τ B ). Porosity may vary through a range of methods. Bed softness may vary in space or time, and changes dramatically from glacier to glacier. An important factor

3025-434: Is called glaciology . Glaciers are important components of the global cryosphere . Glaciers are categorized by their morphology, thermal characteristics, and behavior. Alpine glaciers form on the crests and slopes of mountains. A glacier that fills a valley is called a valley glacier , or alternatively, an alpine glacier or mountain glacier . A large body of glacial ice astride a mountain, mountain range, or volcano

3146-416: Is called rock flour and is made up of rock grains between 0.002 and 0.00625 mm in size. Abrasion leads to steeper valley walls and mountain slopes in alpine settings, which can cause avalanches and rock slides, which add even more material to the glacier. Glacial abrasion is commonly characterized by glacial striations . Glaciers produce these when they contain large boulders that carve long scratches in

3267-647: Is higher, and the mountains above 5,000 m (16,400 ft) usually have permanent snow. Even at high latitudes, glacier formation is not inevitable. Areas of the Arctic , such as Banks Island , and the McMurdo Dry Valleys in Antarctica are considered polar deserts where glaciers cannot form because they receive little snowfall despite the bitter cold. Cold air, unlike warm air, is unable to transport much water vapor. Even during glacial periods of

3388-471: Is natural, or the result of clearing which began during the Incan period. Regardless, in modern times , the clearance has accelerated, and the trees are now considered highly endangered , with some believing that as little as 10% of the original woodland remains. The Andes are rich in fauna: With almost 1,000 species, of which roughly 2/3 are endemic to the region, the Andes are the most important region in

3509-897: Is termed an ice cap or ice field . Ice caps have an area less than 50,000 km (19,000 sq mi) by definition. Glacial bodies larger than 50,000 km (19,000 sq mi) are called ice sheets or continental glaciers . Several kilometers deep, they obscure the underlying topography. Only nunataks protrude from their surfaces. The only extant ice sheets are the two that cover most of Antarctica and Greenland. They contain vast quantities of freshwater, enough that if both melted, global sea levels would rise by over 70 m (230 ft). Portions of an ice sheet or cap that extend into water are called ice shelves ; they tend to be thin with limited slopes and reduced velocities. Narrow, fast-moving sections of an ice sheet are called ice streams . In Antarctica, many ice streams drain into large ice shelves . Some drain directly into

3630-1647: Is the largest city of all Andean countries. It is the seat of the Andean Community of Nations . La Paz , Bolivia 's seat of government, is the highest capital city in the world, at an elevation of approximately 3,650 m (11,975 ft). Parts of the La Paz conurbation, including the city of El Alto , extend up to 4,200 m (13,780 ft). Other cities in or near the Andes include Bariloche , Catamarca , Jujuy , Mendoza , Salta , San Juan , Tucumán , and Ushuaia in Argentina; Calama and Rancagua in Chile; Cochabamba , Oruro , Potosí , Sucre , Tarija , and Yacuiba in Bolivia; Arequipa , Cajamarca , Cusco , Huancayo , Huánuco , Huaraz , Juliaca , and Puno in Peru; Ambato , Cuenca , Ibarra , Latacunga , Loja , Riobamba , and Tulcán in Ecuador; Armenia , Cúcuta , Bucaramanga , Duitama , Ibagué , Ipiales , Manizales , Palmira , Pasto , Pereira , Popayán , Sogamoso , Tunja , and Villavicencio in Colombia; and Barquisimeto , La Grita , Mérida , San Cristóbal , Tovar, Trujillo , and Valera in Venezuela. The cities of Caracas , Valencia , and Maracay are in

3751-413: Is the region where there is a net loss in glacier mass. The upper part of a glacier, where accumulation exceeds ablation, is called the accumulation zone . The equilibrium line separates the ablation zone and the accumulation zone; it is the contour where the amount of new snow gained by accumulation is equal to the amount of ice lost through ablation. In general, the accumulation zone accounts for 60–70% of

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3872-402: Is the underlying geology; glacial speeds tend to differ more when they change bedrock than when the gradient changes. Further, bed roughness can also act to slow glacial motion. The roughness of the bed is a measure of how many boulders and obstacles protrude into the overlying ice. Ice flows around these obstacles by melting under the high pressure on their stoss side ; the resultant meltwater

3993-552: Is then forced into the cavity arising in their lee side , where it re-freezes. As well as affecting the sediment stress, fluid pressure (p w ) can affect the friction between the glacier and the bed. High fluid pressure provides a buoyancy force upwards on the glacier, reducing the friction at its base. The fluid pressure is compared to the ice overburden pressure, p i , given by ρgh. Under fast-flowing ice streams, these two pressures will be approximately equal, with an effective pressure (p i – p w ) of 30 kPa; i.e. all of

4114-404: The 2010 Maule earthquake (M8.8), the 2015 Illapel earthquake (M8.2), and the 1960 Valdivia earthquake (M9.5), which as of 2024 was the strongest ever recorded on seismometers. The amount, magnitude, and type of seismic activity varies greatly along the subduction zone. These differences are due to a wide range of factors, including friction between the plates, angle of subduction, buoyancy of

4235-682: The Americas and Antarctica . The etymology of the word Andes has been debated. The majority consensus is that it derives from the Quechua word anti "east" as in Antisuyu (Quechua for "east region"), one of the four regions of the Inca Empire . The term cordillera comes from the Spanish word cordel "rope" and is used as a descriptive name for several contiguous sections of

4356-456: The Andean cock-of-the-rock , while mixed-species flocks dominated by tanagers and furnariids are commonly seen—in contrast to several vocal but typically- cryptic species of wrens , tapaculos , and antpittas . A number of species such as the royal cinclodes and white-browed tit-spinetail are associated with Polylepis , and consequently also threatened . The Andes Mountains form

4477-993: The Andes , the Himalayas , the Rocky Mountains , the Caucasus , Scandinavian Mountains , and the Alps . Snezhnika glacier in Pirin Mountain, Bulgaria with a latitude of 41°46′09″ N is the southernmost glacial mass in Europe. Mainland Australia currently contains no glaciers, although a small glacier on Mount Kosciuszko was present in the last glacial period . In New Guinea, small, rapidly diminishing, glaciers are located on Puncak Jaya . Africa has glaciers on Mount Kilimanjaro in Tanzania, on Mount Kenya , and in

4598-592: The Caribbean Sea off the coast of Venezuela, were formerly thought to represent the submerged peaks of the extreme northern edge of the Andes range, but ongoing geological studies indicate that such a simplification does not do justice to the complex tectonic boundary between the South American and Caribbean plates . The Andes are an orogenic belt of mountains along the Pacific Ring of Fire ,

4719-535: The Cenozoic . Tectonic forces above the subduction zone along the entire west coast of South America where the Nazca Plate and a part of the Antarctic Plate are sliding beneath the South American Plate continue to produce an ongoing orogenic event resulting in minor to major earthquakes and volcanic eruptions to this day. Many high-magnitude earthquakes have been recorded in the region, such as

4840-644: The Faroe and Crozet Islands were completely glaciated. The permanent snow cover necessary for glacier formation is affected by factors such as the degree of slope on the land, amount of snowfall and the winds. Glaciers can be found in all latitudes except from 20° to 27° north and south of the equator where the presence of the descending limb of the Hadley circulation lowers precipitation so much that with high insolation snow lines reach above 6,500 m (21,330 ft). Between 19˚N and 19˚S, however, precipitation

4961-760: The Himalayas , Andes , and a few high mountains in East Africa, Mexico, New Guinea and on Zard-Kuh in Iran. With more than 7,000 known glaciers, Pakistan has more glacial ice than any other country outside the polar regions. Glaciers cover about 10% of Earth's land surface. Continental glaciers cover nearly 13 million km (5 million sq mi) or about 98% of Antarctica 's 13.2 million km (5.1 million sq mi), with an average thickness of ice 2,100 m (7,000 ft). Greenland and Patagonia also have huge expanses of continental glaciers. The volume of glaciers, not including

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5082-507: The Quaternary , Manchuria , lowland Siberia , and central and northern Alaska , though extraordinarily cold, had such light snowfall that glaciers could not form. In addition to the dry, unglaciated polar regions, some mountains and volcanoes in Bolivia, Chile and Argentina are high (4,500 to 6,900 m or 14,800 to 22,600 ft) and cold, but the relative lack of precipitation prevents snow from accumulating into glaciers. This

5203-535: The Rwenzori Mountains . Oceanic islands with glaciers include Iceland, several of the islands off the coast of Norway including Svalbard and Jan Mayen to the far north, New Zealand and the subantarctic islands of Marion , Heard , Grande Terre (Kerguelen) and Bouvet . During glacial periods of the Quaternary, Taiwan , Hawaii on Mauna Kea and Tenerife also had large alpine glaciers, while

5324-642: The Tropical Andes , the Dry Andes , and the Wet Andes . The Andes are the highest mountain range which is outside of Asia . The range's highest peak, Argentina's Aconcagua , rises to an elevation of about 6,961 m (22,838 ft) above sea level. The peak of Chimborazo in the Ecuadorian Andes is farther from the Earth's center than any other location on the Earth's surface, due to

5445-582: The Venezuelan Coastal Range , which is a debatable extension of the Andes at the northern extremity of South America. Cities and large towns are connected with asphalt -paved roads, while smaller towns are often connected by dirt roads, which may require a four-wheel-drive vehicle. The rough terrain has historically put the costs of building highways and railroads that cross the Andes out of reach of most neighboring countries, even with modern civil engineering practices. For example,

5566-674: The War of the Pacific between Chile and the allied Bolivia and Peru, in a diplomatic deal to keep Peru out of the war. The Chilean Army and Chilean Navy defeated the combined forces of Bolivia and Peru, and Chile took over Bolivia's only province on the Pacific Coast, some land from Peru that was returned to Peru decades later. Bolivia has been completely landlocked ever since. It mostly uses seaports in eastern Argentina and Uruguay for international trade because its diplomatic relations with Chile have been suspended since 1978. Because of

5687-602: The equatorial bulge resulting from the Earth's rotation . The world's highest volcanoes are in the Andes, including Ojos del Salado on the Chile-Argentina border, which rises to 6,893 m (22,615 ft). The Andes are also part of the American Cordillera , a chain of mountain ranges ( cordillera ) that consists of an almost continuous sequence of mountain ranges that form the western "backbone" of

5808-517: The longest continental mountain range in the world, forming a continuous highland along the western edge of South America . The range is 8,900 km (5,530 mi) long and 200 to 700 km (124 to 435 mi) wide (widest between 18°S and 20°S latitude ) and has an average height of about 4,000 m (13,123 ft). The Andes extend from South to North through seven South American countries: Argentina , Chile , Bolivia , Peru , Ecuador , Colombia , and Venezuela . Along their length,

5929-483: The rodent order, inhabit the Andes' alpine regions. The Andean condor , the largest bird of its kind in the Western Hemisphere , occurs throughout much of the Andes but generally in very low densities. Other animals found in the relatively open habitats of the high Andes include the huemul , cougar , foxes in the genus Pseudalopex , and, for birds, certain species of tinamous (notably members of

6050-703: The 1,000-kilometer-wide (620 mi) Drake Passage lie the mountains of the Antarctic Peninsula south of the Scotia Plate , which appear to be a continuation of the Andes chain. The far east regions of the Andes experience a series of changes resulting from the Andean orogeny. Parts of the Sunsás Orogen in Amazonian craton disappeared from the surface of the earth, being overridden by

6171-448: The 1990s and 2000s. In a study using data from January 1993 through October 2005, more events were detected every year since 2002, and twice as many events were recorded in 2005 as there were in any other year. Ogives or Forbes bands are alternating wave crests and valleys that appear as dark and light bands of ice on glacier surfaces. They are linked to seasonal motion of glaciers; the width of one dark and one light band generally equals

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6292-469: The Andean peoples are those of the Quechua and Aymara language families. Woodbine Parish and Joseph Barclay Pentland surveyed a large part of the Bolivian Andes from 1826 to 1827. In modern times, the largest cities in the Andes are Bogotá , with a metropolitan population of over ten million, and Santiago , Medellín , Cali , and Quito . Lima is a coastal city adjacent to the Andes and

6413-405: The Andes are tobacco and potatoes . The high-altitude Polylepis forests and woodlands are found in the Andean areas of Colombia , Ecuador , Peru , Bolivia , and Chile . These trees, by locals referred to as Queñua, Yagual, and other names, can be found at altitudes of 4,500 m (14,760 ft) above sea level. It remains unclear if the patchy distribution of these forests and woodlands

6534-510: The Andes are split into several ranges, separated by intermediate depressions . The Andes are the location of several high plateaus —some of which host major cities such as Quito , Bogotá , Cali , Arequipa , Medellín , Bucaramanga , Sucre , Mérida , El Alto , and La Paz . The Altiplano Plateau is the world's second highest after the Tibetan Plateau . These ranges are in turn grouped into three major divisions based on climate:

6655-521: The Andes end at the Pacific Ocean , although the Peru-Chile trench can be considered their ultimate western limit. From a geographical approach, the Andes are considered to have their western boundaries marked by the appearance of coastal lowlands and less-rugged topography. The Andes also contain large quantities of iron ore located in many mountains within the range. The Andean orogen has

6776-462: The Andes such as the Incas have practiced irrigation techniques for over 6,000 years. Because of the mountain slopes, terracing has been a common practice. Terracing, however, was only extensively employed after Incan imperial expansions to fuel their expanding realm. The potato holds a very important role as an internally-consumed staple crop. Maize was also an important crop for these people, and

6897-526: The Andes varies greatly depending on latitude, altitude, and proximity to the sea. Temperature, atmospheric pressure, and humidity decrease in higher elevations. The southern section is rainy and cool, while the central section is dry. The northern Andes are typically rainy and warm, with an average temperature of 18 °C (64 °F) in Colombia . The climate is known to change drastically in rather short distances. Rainforests exist just kilometers away from

7018-542: The Andes, as well as the entire Andean range, and the combined mountain chain along the western part of the North and South American continents. The Andes can be divided into three sections: At the northern end of the Andes, the separate Sierra Nevada de Santa Marta range is often, but not always, treated as part of the Northern Andes. The Leeward Antilles islands Aruba , Bonaire , and Curaçao , which lie in

7139-524: The Andes. The Sierras de Córdoba , where the effects of the ancient Pampean orogeny can be observed, owe their modern uplift and relief to the Andean orogeny in the Tertiary . Further south in southern Patagonia , the onset of the Andean orogeny caused the Magallanes Basin to evolve from being an extensional back-arc basin in the Mesozoic to being a compressional foreland basin in

7260-491: The Incas were defeated in 1532 by an alliance composed of tens of thousands of allies from nations they had subjugated (e.g. Huancas , Chachapoyas , Cañaris ) and a small army of 180 Spaniards led by Francisco Pizarro . One of the few Inca sites the Spanish never found in their conquest was Machu Picchu , which lay hidden on a peak on the eastern edge of the Andes where they descend to the Amazon. The main surviving languages of

7381-478: The Patagonian Orocline. The western rim of the South American Plate has been the place of several pre-Andean orogenies since at least the late Proterozoic and early Paleozoic , when several terranes and microcontinents collided and amalgamated with the ancient cratons of eastern South America, by then the South American part of Gondwana . The formation of the modern Andes began with

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7502-412: The advance of many alpine glaciers between 1950 and 1985, but since 1985 glacier retreat and mass loss has become larger and increasingly ubiquitous. Glaciers move downhill by the force of gravity and the internal deformation of ice. At the molecular level, ice consists of stacked layers of molecules with relatively weak bonds between layers. When the amount of strain (deformation) is proportional to

7623-520: The air from the snow turns it into "glacial ice". This glacial ice will fill the cirque until it "overflows" through a geological weakness or vacancy, such as a gap between two mountains. When the mass of snow and ice reaches sufficient thickness, it begins to move by a combination of surface slope, gravity, and pressure. On steeper slopes, this can occur with as little as 15 m (49 ft) of snow-ice. In temperate glaciers, snow repeatedly freezes and thaws, changing into granular ice called firn . Under

7744-430: The amount of melting at surface of the glacier, the faster the ice will flow. Basal sliding is dominant in temperate or warm-based glaciers. The presence of basal meltwater depends on both bed temperature and other factors. For instance, the melting point of water decreases under pressure, meaning that water melts at a lower temperature under thicker glaciers. This acts as a "double whammy", because thicker glaciers have

7865-713: The annual movement of the glacier. Ogives are formed when ice from an icefall is severely broken up, increasing ablation surface area during summer. This creates a swale and space for snow accumulation in the winter, which in turn creates a ridge. Sometimes ogives consist only of undulations or color bands and are described as wave ogives or band ogives. Glaciers are present on every continent and in approximately fifty countries, excluding those (Australia, South Africa) that have glaciers only on distant subantarctic island territories. Extensive glaciers are found in Antarctica, Argentina, Chile, Canada, Pakistan, Alaska, Greenland and Iceland. Mountain glaciers are widespread, especially in

7986-592: The area of the maximum width of the Altiplano Plateau , and according to Isacks (1988) the Orocline is related to crustal shortening . The specific point at 18° S where the coastline bends is known as the Arica Elbow. Further south lies the Maipo Orocline, a more subtle orocline between 30° S and 38°S with a seaward-concave break in the trend at 33° S. Near the southern tip of the Andes lies

8107-477: The bay is spelled "Latuya".) The same topography that leads to the heavy tidal currents also created the tsunami with the highest runup against a hillside in recorded history. On the night of July 9, 1958, an earthquake caused a landslide in the Gilbert Inlet at the head of the bay, generating a massive megatsunami which had sufficient energy to run up the hill slope just opposite of the landslide to

8228-432: The bedrock has frequent fractures on the surface, glacial erosion rates tend to increase as plucking is the main erosive force on the surface; when the bedrock has wide gaps between sporadic fractures, however, abrasion tends to be the dominant erosive form and glacial erosion rates become slow. Glaciers in lower latitudes tend to be much more erosive than glaciers in higher latitudes, because they have more meltwater reaching

8349-445: The bedrock. By mapping the direction of the striations, researchers can determine the direction of the glacier's movement. Similar to striations are chatter marks , lines of crescent-shape depressions in the rock underlying a glacier. They are formed by abrasion when boulders in the glacier are repeatedly caught and released as they are dragged along the bedrock. The rate of glacier erosion varies. Six factors control erosion rate: When

8470-571: The created ice's density. The word glacier is a loanword from French and goes back, via Franco-Provençal , to the Vulgar Latin glaciārium , derived from the Late Latin glacia , and ultimately Latin glaciēs , meaning "ice". The processes and features caused by or related to glaciers are referred to as glacial. The process of glacier establishment, growth and flow is called glaciation . The corresponding area of study

8591-467: The deep profile of fjords , which can reach a kilometer in depth as ice is topographically steered into them. The extension of fjords inland increases the rate of ice sheet thinning since they are the principal conduits for draining ice sheets. It also makes the ice sheets more sensitive to changes in climate and the ocean. Although evidence in favor of glacial flow was known by the early 19th century, other theories of glacial motion were advanced, such as

8712-483: The deformation to become a plastic flow rather than elastic. Then, the glacier will begin to deform under its own weight and flow across the landscape. According to the Glen–Nye flow law , the relationship between stress and strain, and thus the rate of internal flow, can be modeled as follows: where: The lowest velocities are near the base of the glacier and along valley sides where friction acts against flow, causing

8833-399: The dry climate that reduced the disturbing actions of meteoric water . The dry climate in the central western Andes has also led to the creation of extensive saltpeter deposits which were extensively mined until the invention of synthetic nitrates . Yet another result of the dry climate are the salars of Atacama and Uyuni , the former being the largest source of lithium and the latter

8954-532: The dry season (winter) possible and allows the cultivation of frost-resistant vegetable crops like onion and carrot . The Andes rose to fame for their mineral wealth during the Spanish conquest of South America . Although Andean Amerindian peoples crafted ceremonial jewelry of gold and other metals, the mineralizations of the Andes were first mined on a large scale after the Spanish arrival. Potosí in present-day Bolivia and Cerro de Pasco in Peru were among

9075-468: The entrance reach 9.4 km/h (5.1 kn). The entrance is considered dangerous to navigation, especially when the tidal currents are running, but the interior of the bay provides good protection to anchored ships. Lituya Bay is also famous for four recorded tsunamis , in 1854, 1899, 1936, and 1958. The bay is mentioned in Jack London 's short story, "The Unexpected". (In that story, the name of

9196-418: The essentially correct explanation in the 1840s, although it was several decades before it was fully accepted. The top 50 m (160 ft) of a glacier are rigid because they are under low pressure . This upper section is known as the fracture zone and moves mostly as a single unit over the plastic-flowing lower section. When a glacier moves through irregular terrain, cracks called crevasses develop in

9317-501: The establishment of the century-long Inca Empire . This all changed in the 16th century, when the Spanish conquistadors colonized the mountains in advance of the mining economy. In the tide of anti-imperialist nationalism, the Andes became the scene of a series of independence wars in the 19th century, when rebel forces swept through the region to overthrow Spanish colonial rule. Since then, many former Spanish territories have become five independent Andean states. The climate in

9438-705: The events of the Triassic , when Pangaea began the breakup that resulted in developing several rifts . The development continued through the Jurassic Period. It was during the Cretaceous Period that the Andes began to take their present form, by the uplifting , faulting , and folding of sedimentary and metamorphic rocks of the ancient cratons to the east. The rise of the Andes has not been constant, as different regions have had different degrees of tectonic stress, uplift, and erosion . Across

9559-423: The extreme in the slopes near the virtually-lifeless Atacama Desert. About 30,000 species of vascular plants live in the Andes, with roughly half being endemic to the region, surpassing the diversity of any other hotspot . The small tree Cinchona pubescens , a source of quinine which is used to treat malaria , is found widely in the Andes as far south as Bolivia. Other important crops that originated from

9680-464: The forelands of the Atacama Desert , some of the largest porphyry copper mineralizations occur, making Chile and Peru the first- and second-largest exporters of copper in the world. Porphyry copper in the western slopes of the Andes has been generated by hydrothermal fluids (mostly water) during the cooling of plutons or volcanic systems. The porphyry mineralization further benefited from

9801-475: The fracture zone. Crevasses form because of differences in glacier velocity. If two rigid sections of a glacier move at different speeds or directions, shear forces cause them to break apart, opening a crevasse. Crevasses are seldom more than 46 m (150 ft) deep but, in some cases, can be at least 300 m (1,000 ft) deep. Beneath this point, the plasticity of the ice prevents the formation of cracks. Intersecting crevasses can create isolated peaks in

9922-555: The genus Nothoprocta ), Andean goose , giant coot , flamingos (mainly associated with hypersaline lakes), lesser rhea , Andean flicker , diademed sandpiper-plover , miners , sierra-finches and diuca-finches . Lake Titicaca hosts several endemics, among them the highly endangered Titicaca flightless grebe and Titicaca water frog . A few species of hummingbirds , notably some hillstars , can be seen at altitudes above 4,000 m (13,100 ft), but far higher diversities can be found at lower altitudes, especially in

10043-524: The glacial base and facilitate sediment production and transport under the same moving speed and amount of ice. Material that becomes incorporated in a glacier is typically carried as far as the zone of ablation before being deposited. Glacial deposits are of two distinct types: Andes The Andes ( / ˈ æ n d iː z / AN -deez ), Andes Mountains or Andean Mountain Range ( Spanish : Cordillera de los Andes ; Quechua : Anti ) are

10164-453: The glacier to melt, creating a water source that is especially important for plants, animals and human uses when other sources may be scant. However, within high-altitude and Antarctic environments, the seasonal temperature difference is often not sufficient to release meltwater. Since glacial mass is affected by long-term climatic changes, e.g., precipitation , mean temperature , and cloud cover , glacial mass changes are considered among

10285-428: The glacier will be accommodated by motion in the sediments, or if it'll be able to slide. A soft bed, with high porosity and low pore fluid pressure, allows the glacier to move by sediment sliding: the base of the glacier may even remain frozen to the bed, where the underlying sediment slips underneath it like a tube of toothpaste. A hard bed cannot deform in this way; therefore the only way for hard-based glaciers to move

10406-510: The glacier's surface area, more if the glacier calves icebergs. Ice in the accumulation zone is deep enough to exert a downward force that erodes underlying rock. After a glacier melts, it often leaves behind a bowl- or amphitheater-shaped depression that ranges in size from large basins like the Great Lakes to smaller mountain depressions known as cirques . The accumulation zone can be subdivided based on its melt conditions. The health of

10527-512: The glaciers were over ten times longer. On the east side of this section of the Mendozina Andes, they flowed down to 2,060 m (6,759 ft) and on the west side to about 1,220 m (4,003 ft) above sea level. The massifs of Aconcagua (6,961 m (22,838 ft)), Tupungato (6,550 m (21,490 ft)), and Nevado Juncal (6,110 m (20,046 ft)) are tens of kilometres away from each other and were connected by

10648-556: The humid Andean forests (" cloud forests ") growing on slopes in Colombia, Ecuador, Peru, Bolivia, and far northwestern Argentina. These forest-types, which includes the Yungas and parts of the Chocó, are very rich in flora and fauna, although few large mammals exist, exceptions being the threatened mountain tapir , spectacled bear , and yellow-tailed woolly monkey . Birds of humid Andean forests include mountain toucans , quetzals , and

10769-517: The hyperarid Atacama Desert . Rainforests and tropical dry forests used to encircle much of the northern Andes but are now greatly diminished , especially in the Chocó and inter-Andean valleys of Colombia. Opposite the humid Andean slopes are the relatively dry Andean slopes in most of western Peru, Chile, and Argentina. Along with several Interandean Valles , they are typically dominated by deciduous woodland, shrub and xeric vegetation, reaching

10890-619: The ice at the bottom of the glacier move more slowly than ice at the top. In alpine glaciers, friction is also generated at the valley's sidewalls, which slows the edges relative to the center. Mean glacial speed varies greatly but is typically around 1 m (3 ft) per day. There may be no motion in stagnant areas; for example, in parts of Alaska, trees can establish themselves on surface sediment deposits. In other cases, glaciers can move as fast as 20–30 m (70–100 ft) per day, such as in Greenland's Jakobshavn Isbræ . Glacial speed

11011-420: The ice sheets of Antarctica and Greenland, has been estimated at 170,000 km . Glacial ice is the largest reservoir of fresh water on Earth, holding with ice sheets about 69 percent of the world's freshwater. Many glaciers from temperate , alpine and seasonal polar climates store water as ice during the colder seasons and release it later in the form of meltwater as warmer summer temperatures cause

11132-556: The ice to act as a lever that loosens the rock by lifting it. Thus, sediments of all sizes become part of the glacier's load. If a retreating glacier gains enough debris, it may become a rock glacier , like the Timpanogos Glacier in Utah. Abrasion occurs when the ice and its load of rock fragments slide over bedrock and function as sandpaper, smoothing and polishing the bedrock below. The pulverized rock this process produces

11253-488: The ice, called seracs . Crevasses can form in several different ways. Transverse crevasses are transverse to flow and form where steeper slopes cause a glacier to accelerate. Longitudinal crevasses form semi-parallel to flow where a glacier expands laterally. Marginal crevasses form near the edge of the glacier, caused by the reduction in speed caused by friction of the valley walls. Marginal crevasses are largely transverse to flow. Moving glacier ice can sometimes separate from

11374-411: The idea that meltwater, refreezing inside glaciers, caused the glacier to dilate and extend its length. As it became clear that glaciers behaved to some degree as if the ice were a viscous fluid, it was argued that "regelation", or the melting and refreezing of ice at a temperature lowered by the pressure on the ice inside the glacier, was what allowed the ice to deform and flow. James Forbes came up with

11495-418: The increased pressure can facilitate melting. Most importantly, τ D is increased. These factors will combine to accelerate the glacier. As friction increases with the square of velocity, faster motion will greatly increase frictional heating, with ensuing melting – which causes a positive feedback, increasing ice speed to a faster flow rate still: west Antarctic glaciers are known to reach velocities of up to

11616-423: The infrared OH stretching mode of the water molecule. (Liquid water appears blue for the same reason. The blue of glacier ice is sometimes misattributed to Rayleigh scattering of bubbles in the ice.) A glacier originates at a location called its glacier head and terminates at its glacier foot, snout, or terminus . Glaciers are broken into zones based on surface snowpack and melt conditions. The ablation zone

11737-609: The la Chasseuse, spit into the ocean, hit by a floating log and sunk but not before its occupants (a married couple, the Swansons) in spite of injuries, managed to board a skiff ultimately to be rescued. The third boat, the Edrie , crewed by father and son the Ulriches, was anchored at the opposite side of the bay entrance. The father, Howard, turned the boat to face the wave, which picked her up, snapped her anchor chain, carried her above

11858-555: The larger glaciers descend to sea level. The Andes of Chile and Argentina can be divided into two climatic and glaciological zones: the Dry Andes and the Wet Andes . Since the Dry Andes extend from the latitudes of the Atacama Desert to the area of the Maule River , precipitation is more sporadic, and there are strong temperature oscillations. The line of equilibrium may shift drastically over short periods of time, leaving

11979-523: The main crossover of the Andes between Argentina and Chile is still accomplished through the Paso Internacional Los Libertadores . Only recently have the ends of some highways that came rather close to one another from the east and the west been connected. Much of the transportation of passengers is done via aircraft. However, there is one railroad that connects Chile with Peru via the Andes, and there are others that make

12100-679: The most deformation. Velocity increases inward toward the center line and upward, as the amount of deformation decreases. The highest flow velocities are found at the surface, representing the sum of the velocities of all the layers below. Because ice can flow faster where it is thicker, the rate of glacier-induced erosion is directly proportional to the thickness of overlying ice. Consequently, pre-glacial low hollows will be deepened and pre-existing topography will be amplified by glacial action, while nunataks , which protrude above ice sheets, barely erode at all – erosion has been estimated as 5 m per 1.2 million years. This explains, for example,

12221-445: The most sensitive indicators of climate change and are a major source of variations in sea level . A large piece of compressed ice, or a glacier, appears blue , as large quantities of water appear blue , because water molecules absorb other colors more efficiently than blue. The other reason for the blue color of glaciers is the lack of air bubbles. Air bubbles, which give a white color to ice, are squeezed out by pressure increasing

12342-576: The nearly-7,000-metre (22,966 ft) highest mountains of the Andes. This dry steppe climate is considered to be typical of the subtropical position at 32–34° S. The valley bottoms have no woods, just dwarf scrub. The largest glaciers, for example the Plomo Glacier and the Horcones Glaciers, do not even reach 10 km (6.2 mi) in length and have only insignificant ice thickness. At glacial times, however, c. 20,000 years ago,

12463-725: The pooling of meltwater at the base of the glacier  — perhaps delivered from a supraglacial lake  — or the simple accumulation of mass beyond a critical "tipping point". Temporary rates up to 90 m (300 ft) per day have occurred when increased temperature or overlying pressure caused bottom ice to melt and water to accumulate beneath a glacier. In glaciated areas where the glacier moves faster than one km per year, glacial earthquakes occur. These are large scale earthquakes that have seismic magnitudes as high as 6.1. The number of glacial earthquakes in Greenland peaks every year in July, August, and September and increased rapidly in

12584-410: The pressure of the layers of ice and snow above it, this granular ice fuses into denser firn. Over a period of years, layers of firn undergo further compaction and become glacial ice. Glacier ice is slightly more dense than ice formed from frozen water because glacier ice contains fewer trapped air bubbles. Glacial ice has a distinctive blue tint because it absorbs some red light due to an overtone of

12705-402: The rainy season (summer), part of the rangeland is used for cropping (mainly potatoes, barley, broad beans, and wheat). Irrigation is helpful in advancing the sowing data of the summer crops, which guarantees an early yield in periods of food shortage. Also, by early sowing, maize can be cultivated higher up in the mountains (up to 3,800 m (12,500 ft)). In addition, it makes cropping in

12826-460: The same connection via southern Bolivia. There are multiple highways in Bolivia that cross the Andes. Some of these were built during a period of war between Bolivia and Paraguay , in order to transport Bolivian troops and their supplies to the war front in the lowlands of southeastern Bolivia and western Paraguay. For decades, Chile claimed ownership of land on the eastern side of the Andes. However, these claims were given up in about 1870 during

12947-567: The sea, often with an ice tongue , like Mertz Glacier . Tidewater glaciers are glaciers that terminate in the sea, including most glaciers flowing from Greenland, Antarctica, Baffin , Devon , and Ellesmere Islands in Canada, Southeast Alaska , and the Northern and Southern Patagonian Ice Fields . As the ice reaches the sea, pieces break off or calve, forming icebergs . Most tidewater glaciers calve above sea level, which often results in

13068-721: The snow-covered peak of Cotopaxi . The mountains have a large effect on the temperatures of nearby areas. The snow line depends on the location. It is between 4,500 and 4,800 m (14,764 and 15,748 ft) in the tropical Ecuadorian, Colombian, Venezuelan, and northern Peruvian Andes, rising to 4,800–5,200 m (15,748–17,060 ft) in the drier mountains of southern Peru and northern Chile south to about 30°S before descending to 4,500 m (14,760 ft) on Aconcagua at 32°S , 2,000 m (6,600 ft) at 40°S , 500 m (1,640 ft) at 50°S , and only 300 m (980 ft) in Tierra del Fuego at 55°S ; from 50°S, several of

13189-409: The stagnant ice above, forming a bergschrund . Bergschrunds resemble crevasses but are singular features at a glacier's margins. Crevasses make travel over glaciers hazardous, especially when they are hidden by fragile snow bridges . Below the equilibrium line, glacial meltwater is concentrated in stream channels. Meltwater can pool in proglacial lakes on top of a glacier or descend into the depths of

13310-423: The stress being applied, ice will act as an elastic solid. Ice needs to be at least 30 m (98 ft) thick to even start flowing, but once its thickness exceeds about 50 m (160 ft) (160 ft), stress on the layer above will exceeds the inter-layer binding strength, and then it'll move faster than the layer below. This means that small amounts of stress can result in a large amount of strain, causing

13431-526: The subducting plate, rate of subduction, and hydration value of the mantle material. The highest rate of seismic activity is observed in the central portion of the boundary, between 33°S and 35°S. In this area, the angle of subduction is very low, meaning the subducting plate is nearly horizontal. Studies of mantle hydration across the subduction zone have shown a correlation between increased material hydration and lower-magnitude, more-frequent seismic activity. Zones exhibiting dehydration instead are thought to have

13552-637: The subduction of the Nazca Plate and the Antarctic Plate . To the east, the Andes range is bounded by several sedimentary basins , such as the Orinoco Basin , the Amazon Basin , the Madre de Dios Basin, and the Gran Chaco , that separate the Andes from the ancient cratons in eastern South America. In the south, the Andes share a long boundary with the former Patagonia Terrane . To the west,

13673-438: The surface snowpack may experience seasonal melting. A subpolar glacier includes both temperate and polar ice, depending on the depth beneath the surface and position along the length of the glacier. In a similar way, the thermal regime of a glacier is often described by its basal temperature. A cold-based glacier is below freezing at the ice-ground interface and is thus frozen to the underlying substrate. A warm-based glacier

13794-452: The tortuous terrain in places, villages and towns in the mountains—to which travel via motorized vehicles is of little use—are still located in the high Andes of Chile, Bolivia, Peru, and Ecuador . Locally, the relatives of the camel , the llama , and the alpaca continue to carry out important uses as pack animals, but this use has generally diminished in modern times. Donkeys , mules , and horses are also useful. The ancient peoples of

13915-436: The trees but then washed her back into the bay with no major damage. William A. Swanson and Howard G. Ulrich provided accounts of what they observed. Based on Swanson's description of the length of time it took the wave to reach his boat after overtopping Cenotaph Island near the bay's entrance, the wave may have been traveling 120 mph (190 km/h). When it reached the open sea, however, it dissipated quickly. This incident

14036-477: The uplift of the Andes created a rain shadow on the western fringes of Chile, ocean currents and prevailing winds carried moisture away from the Chilean coast. This caused some areas of the subduction zone to be sediment-starved, causing excess friction and an increased rate of compressed coastal uplift. The main cause of the rise of the Andes is the compression of the western rim of the South American Plate due to

14157-417: The weight of the ice is supported by the underlying water, and the glacier is afloat. Glaciers may also move by basal sliding , where the base of the glacier is lubricated by the presence of liquid water, reducing basal shear stress and allowing the glacier to slide over the terrain on which it sits. Meltwater may be produced by pressure-induced melting, friction or geothermal heat . The more variable

14278-642: The world for amphibians . The diversity of animals in the Andes is high, with almost 600 species of mammals (13% endemic), more than 1,700 species of birds (about 1/3 endemic), more than 600 species of reptiles (about 45% endemic), and almost 400 species of fish (about 1/3 endemic). The vicuña and guanaco can be found living in the Altiplano , while the closely related domesticated llama and alpaca are widely kept by locals as pack animals and for their meat and wool . The crepuscular (active during dawn and dusk) chinchillas , two threatened members of

14399-470: The world's largest reserve of the element. Early Mesozoic and Neogene plutonism in Bolivia's Cordillera Central created the Bolivian tin belt as well as the famous, now-mostly-depleted, deposits of Cerro Rico de Potosí . The Andes Mountains, initially inhabited by hunter-gatherers , experienced the development of agriculture and the rise of politically centralized civilizations , which culminated in

14520-696: Was the first direct evidence and eyewitness report of the existence of megatsunamis. Glacier A glacier ( US : / ˈ ɡ l eɪ ʃ ər / ; UK : / ˈ ɡ l æ s i ər , ˈ ɡ l eɪ s i ər / ) is a persistent body of dense ice that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries . It acquires distinguishing features, such as crevasses and seracs , as it slowly flows and deforms under stresses induced by its weight. As it moves, it abrades rock and debris from its substrate to create landforms such as cirques , moraines , or fjords . Although

14641-408: Was used for the production of chicha , important to Andean native people. Currently, tobacco , cotton , and coffee are the main export crops. Coca , despite eradication programs in some countries, remains an important crop for legal local use in a mildly stimulating herbal tea , and illegally for the production of cocaine . In unirrigated land, pasture is the most common type of land use. In

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